Process and apparatus for casting metals and ceramic masses according to the centrifuging method



Sept. 15, 1931. C.

PROCESS AND APPARATUS MASSES ACCORDING TO THE GEN FRITZSCHE FOR CASTING METALS AND CERAMIC TRIFUGING METHOD Filed March 15, 1929 ,9 ll i| (ID 3 v .s i; 1a 9 13 2 Patented Sept. 15, 1931 'PATE NT OFFICE GUR'J. FRITZSCHE, OF LEIPZIG,

PROCESS AND APPARATUS FOR CASTING METALS AND CERAMIC 'MASSES ACCORDING TO THE CENTRIFUGING METHOD Application filed March 15, 1929, Serial No. 347,413, and in Germany March 21, 1928.

Several inconveniences which hitherto could not be obviated are connected with the casting of all metals and ceramic masses in hollow moulds. The cast of metal is not sufficiently dense or homogenous. Blisters or funnels are formed and the contours of the work are not sufficiently sharp on the cast piece. These inconveniences are specially perceivable at precision casting of a body the surface of which is of complicated consist in heating the material to be molten V at the centrifuging process from above by a narrow flame or by an electric arc. The small quantity of casting metal or ceramic mass solidifies almost instantaneously. The

casting material has -no time to fill properly a complicated hollow mould or to flow properly into hollow moulds of quite narrow inp ner width. The thinner the article to be cast is, the more rapidly solidifies the molten material. As the air has sometimes not sufficient time to escape from the mould, pores are produced, and slag formations are sometimes enclosed by the suddenly solidifying molten material. Owing to the rapid solidifying of the material it is impossible that a homogenous structure of a cast body develops. The cast is brittle and of inaccurate and 9 not sharp contours.

'The higher the smelting point of the casting material, the more serious becomes the above mentioned inconveniences, this being the reason why many metals possessing high '45 smelting points cannot be used for casting dental articles.

The metal to be cast is commonly molten by the open narrow flame in the casting funnel, the hollow mould under the funnel remaining much colder so that the inconven- I have discovered, that the fact that the hollow mould is cold is a cause for all said inconveniences, as all commonly used casting methods are based on the principle 'to heat the material for casting as strongly as possible and then to cast the same into a hollow mould which is always considerably colder than the heated material. According to the invention the centrifugmg of the molten material is carried out in a room heated to uniform temperature and only then when the molten material, the castlng implements, i. e. the casting box, the embedding material, the hollow mould, the cast- 1ng funnel, the casting hole and the like, have been heated to the same temperature, the cooling of the heated casting utensilsbeing effected uniformly after the casting by accordmgly regulating the electric heating current.

An apparatus for carrying out the improved method is illustrated by'way of example 1n the accompanying drawings in which: i Fig. 1 shows the casting mould in elevation.

Fig. 2 is a longitudinal section-through the apparatus.

Fig. 3 is a section on line 3-3 of Fig. 2. The article 12 to be cast is modelled as usual 1n wax, this 'model being embedded in a refractory mass .13 contained in a box 1 1 (Fig. 4). The casting channel 15 communicates with the casting funnel 16 containingthe material 17 to be cast. Air channels 18 are provided. The mould13 is placed in an electrio muflle furnace. This muflle furnace consists of a chamotte mufile 2. On the bottom, the ceiling and, if necessary, on the side walls -of the muflie 2 electric resistance heating bodies 1, for instance silicium rods, are arranged. The heating bodies on the bottom of the furnace are covered by a plate 18, for

instance ofporcelain, on which the moiild 13 i is placed. The electric heating bodies might be arranged vertical or circular. The main condition is, that the hollow space 7 in the furnace 2 is uniformly heated by the electric heating bodies.

The furnace 2 isfixed on the end of an arm from a source of current 'nace 2 is vertical.

In order that during the furnace 2 the current supply to the electric heating resistances 1 be not interrupted, col

lector rings 4 are arranged on the axle 20. from which the current is supplied to the heating bodies 1 through leads 8, 9. ,The current is supplied to the collectof rings 4 by means of brushes 5 to which it is supplied %5 through an adjustable resistance 6 and w res 10 and 11.

The material 17 in the funnel 10 is heated until it is thinly liquid, the mould 13 being heated to the same temperature. The-muflie furnace 2, the hollow mould 12 in the same and the casting utensils 13, 14, 15 are rotated around the stationaryaxle 20, the electric heating being not interrupted so that the thinly liquid material has suflicient timeto flow into the narrow hollow spaces of the mould 12. The electric heating is gradually reduced and then shut off, the mufile furnace continuing for some time to be centrifuged gugil the cast material has gradually solidi- The cast body cools gradually in the closed' 'mullie furnace.

According to the method described castings from any metals can be produced which are castable, as it is possible to obtain in the 'closed mufile furnace any casting temperature. The same is valid for ceramic masses. This possibility has hitherto not existed. When the electric heating is only quite central space, a two part mould arranged on.

the bottom of the central space concentrical- --ly\to the center axis of said electric furnace rotation of the ncl shaped charging aperture adapted to acand having in its upper part a central funcommodate the material to be melted, electric resistance heating bodies on the bottom, ceiling and side walls of su id furnace around said' mould adapted to uniformly heat said central space and therefore said mould and the material in the funnel shaped aperture of the upper part of'said mould, collector rings on the shaft of said centrifuge, leads connecting said collector rings with said electric heating bodies, a source of current, brushes for supplying current tosaid collector rings, I w1res connectlng said brushes with sa dsource of current, and an adjustable resistance insaid wires. I

In testimony whereof I aflix my signature.

CURT FRITZSCHE.

gradually cut out malleable castings are obtained such as could hitherto not be obtained by the commonly used dental casting methods.

The method described is specially adapted for dental castings like plates for sets of artificial teeth, fillings, crowns, bridges, regulating work and the like. 4

The method described is also adapted for other purposes, requiring precision casting, for instance for articles of art and articles for use or parts of such, specially for small size articles having a complicated surface and very accurate contours. v

I claim:

1. A method of casting metals and ceramic masses consisting in simultaneously and uniformly heating the casting utensils and material to be cast, in centrifuging the material when fused into said heated utensils having the same temperature as the fused material, and in uniformly cooling said utensils to- 

